Electromagnetic device with composite structure heat transfer flow path

ABSTRACT

Electromagnetic components are provided with a heat exchange mechanism. For example, a fluid-cooled electromagnetic field-functioning device, such as a motor, generator, transformer, solenoid or relay, comprises one or more electrical conductors. A monolithic body of phase change material substantially encapsulates the conductors or an inductor. At least one liquid-tight coolant channel is also substantially encapsulated within the body of phase change material. The coolant channel may be part of a heat pipe or cold plate. The coolant channel may be made by molding a conduit into the body, using a “lost wax” molding process, or injecting gas into the molten phase change material while it is in the mold. The coolant channel may also be formed at the juncture between the body and a cover over the body.

FIELD OF THE INVENTION

The present invention relates generally to electromagnetic devices thatinclude heat exchange mechanisms. It relates particularly to motors,generators, transformers, relays and solenoids that are cooled by afluid coolant. The devices can be used in various electronic products,such as a motor for hard disc drive or other consumer electronic device,a pump motor, a motor/generator used in a hybrid electric vehicle, amotor used in an air blower and a solenoid used in a fuel injector orliquid flow valve.

BACKGROUND OF THE INVENTION

The present invention utilizes aspects of Applicant's earlierinventions, some of which are repeated herein. U.S. Pat. Nos. 6,362,554;6,753,682 and 6,911,166, which are hereby incorporated by reference,further disclose some of these concepts.

An example of a conventional motor 1 is shown in FIG. 1. The motor 1includes a base 2 which is usually made from die cast aluminum, a stator4, a shaft 6, bearings 7 and a disc support member 8, also referred toas a hub. A magnet 3 and flux return ring 5 are attached to the discsupport member 8. The stator 4 is separated from the base 2 using aninsulator (not shown) and attached to the base 2 using a glue. Distinctstructures are formed in the base 2 and the disc support member 8 toaccommodate the bearings 7. One end of the shaft 6 is inserted into thebearing 7 positioned in the base 2 and the other end of the shaft 6 isplaced in the bearing 7 located in the hub 8. A separate electricalconnector 9 may also be inserted into the base 2.

Each of these parts must be fixed at predefined tolerances with respectto one another. Accuracy in these tolerances can significantly enhancemotor performance.

An important factor in motor design is the lowering of the operatingtemperature of the motor. Increased motor temperature affects theelectrical efficiency of the motor and bearing life. As temperatureincreases, resistive loses in wire increase, thereby reducing totalmotor power. Furthermore, the Arrhenius equation predicts that thefailure rate of an electrical device is exponentially related to itsoperating temperature. The frictional heat generated by bearingsincreases with speed. Also, as bearings get hot they expand, and thebearing cages get stressed and may deflect, causing non-uniform rotationand the resultant further heat increase. One drawback with existingmotor designs is their limited effective dissipation of the heat, anddifficulty in incorporating heat sinks to aid in heat dissipation. Inaddition, in current motors the operating temperatures generallyincrease as the size of the motor is decreased.

Electromagnetic devices used in electrical products may need to becooled to remove heat generated by operation of the device. It is wellknown that a fluid in the environment of the device can be used to aidcooling. As an example, a method of cooling a motor is to include a fanon the motor shaft. The fan then blows air past the motor. Air, however,has a fairly low heat capacity, and thus cannot carry away as much heatas is sometime generated by the motor. Also, in some applications thereis no place to mount a fan. Other fluids, and liquids in particular,typically have a high enough heat capacity that they can be used tocarry away heat. For example, a water pump driven by a motor uses thewater to cool the pump. The problem with liquids, however, is gettingthem in contact with hot motor surfaces without damaging the motor, andthen collecting them to carry them away. Thus, a need exists for animproved motor that includes an effective and practical way of using aliquid to carry heat away from the motor. Also, a need exits forimproved methods of cooling other electromagnetic components.

Also, there are times when the heat generated by operation of theelectrical device, such as a motor, could be put to a beneficial use ifthere were a way to confine a fluid used in a heat transfer relationshipwith the device so that it could be directed to a point of desired use.Thus, if liquids or gasses could be channeled in such a way that theypicked up heat from an electromagnetic device without damaging thedevice, and then carried that heat to a place where the heat wasdesired, that would be a great benefit.

One difficulty encountered in the design of electrical components isthat various components need to withstand exposure to solvents andparticulates. The environmental agents can corrode the conductors orinductors in the component. In pumps used for movement of corrosiveagents, this can be a particular problem. In hybrid electric vehicleswhere the motor or generator resides inside of the transmission housing,stray metallic debris generated from the transmission gears may bethrown into the windings, damaging them to the point that the device nolonger works.

BRIEF SUMMARY OF THE INVENTION

Electromagnetic devices have been invented which overcome many of theforegoing problems. In one class of devices, a heat transfer fluid flowsthrough the device. In another class of devices, a heat transfer fluidis contained within the device. Encapsulating portions of the device atthe same time a heat exchange mechanism is provided may provide theadditional benefit of protecting the parts from corrosive or otherwisedamaging environments.

In a first aspect, the invention is a fluid-cooled electromagneticfield-functioning device comprising at least one electrical conductor; amonolithic body of injection molded thermoplastic material substantiallyencapsulating the at least one conductor; and a mating component,wherein a heat transfer fluid pathway is defined by at least one channelin the monolithic body covered by the mating component, with at leastone fluid inlet and at least one fluid outlet to the pathway to allowfor passage of heat transfer fluid through the pathway.

In a second aspect, the invention is a fluid-cooled electromagneticfield-functioning device comprising at least one electrical conductor;monolithic body of injection molded thermoplastic material substantiallyencapsulating the at least one conductor; and a mating component,wherein a heat transfer fluid pathway is defined by at least one channelin the monolithic body covered by the mating component, with at leastone fluid inlet and at least one fluid outlet to the pathway to allowfor passage of heat transfer fluid through the pathway.

In a second aspect the invention is a fluid-cooled electromagneticfield-functioning device comprising at least one electrical conductorand at least one inductor; a monolithic body of injection moldedthermoplastic material substantially encapsulating the at least oneinductor; and a mating component, wherein a heat transfer fluid pathwayis defined by at least one channel in the monolithic body covered by themating component, with at least one fluid inlet and at least one fluidoutlet to the pathway to allow for passage of heat transfer fluidthrough the pathway.

In another aspect, the invention is a fluid-cooled electromagneticfield-functioning device comprising one or more electrical conductors; aheat transfer fluid confinement member; and a monolithic body of phasechange material substantially encapsulating both the one or moreconductors and the heat transfer fluid confinement member.

In yet another aspect the invention is a fluid-cooled electromagneticdevice comprising an assembly comprising i) an inductor in operableproximity to at least one conductor that creates at least one magneticfield when electrical current is conducted by the conductor; and ii) abody of a phase change material substantially encapsulating theconductor; and at least one liquid-tight coolant channel substantiallyencapsulated within the body of phase change material.

In still another aspect the invention is a fluid-cooled electromagneticfield-functioning device comprising an inductor and at least oneconductor that creates at least one magnetic field when electricalcurrent is conducted by the conductor; a heat transfer fluid confinementmember containing a heat transfer fluid; and a monolithic body of phasechange material substantially encapsulating at least one of the inductorand the at least one conductor, the monolithic body being in thermalcontact with the heat transfer fluid.

A further aspect of the invention is a method of making a fluid-cooledelectromagnetic field-functioning device comprising the steps ofproviding a core assembly comprising an inductor and at least oneconductor that creates at least one magnetic field when electricalcurrent is conducted by the conductor, substantially encapsulating atleast one of the inductor and the at least one conductor in a body ofphase change material; providing a heat transfer fluid confinementchamber in the body of phase change material; and, adding a heattransfer fluid to the confinement chamber and sealing the chamber toretain the heat transfer fluid in the chamber.

In another aspect the invention is a method of cooling anelectromagnetic field-functioning device wherein the electromagneticfield-functioning device comprises one or more electrical conductors anda monolithic body of phase change material substantially encapsulatingthe one or more conductors, wherein a heat transfer fluid flows througha confined path substantially within the body of phase change materialto transfer heat away from the conductors.

In one embodiment, a motor can be cooled by using a heat pipe embeddedin a body of phase change material that also substantially encapsulatesparts of the motor. In another embodiment, a motor can be cooled bypassing liquid through a coolant channel encased in the body of phasechange material also substantially encapsulating the motor component.The body of phase change material provides a path for the heat to betransferred from the stator to the liquid coolant, where it can becarried away. The liquid is also confined, so that it does not contactother parts of the motor or get randomly discharged from the motor.Besides motors, other electromagnetic field function devices may be madewith coolant channels. The flow path or chamber for the coolant may beformed by injecting gas into the molten thermoplastic after it has beeninjected into a mold but before it solidifies to form the bodyencapsulating the motor component, or component of other electromagneticfield-functioning devices. The foregoing and other features, and theadvantages of the invention, will become further apparent from thefollowing detailed description of the presently preferred embodiments,read in conjunction with the accompanying drawings. The detaileddescription and drawings are merely illustrative of the invention and donot limit the scope of the invention, which is defined by the appendedclaims and equivalents thereof.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exploded, partial cross-sectional and perspective view of aprior art high speed motor.

FIG. 2 is a perspective view of a stator used in a first embodiment ofthe present invention.

FIG. 3 is an exploded, partial cross-sectional and perspective view of ahigh speed motor in accordance with a first embodiment of the presentinvention.

FIG. 4 is a cross-sectional view of the high speed motor of FIG. 3.

FIG. 5 is a schematic drawing of a mold used to make the encapsulatedstator of the motor of FIG. 3.

FIG. 6 is a schematic drawing of the mold of FIG. 5 in a closedposition.

FIG. 7 is an exploded, partial cross-sectional and perspective view of ahigh speed motor in accordance with a second embodiment of the presentinvention.

FIG. 8 is a cross-sectional view of a high speed motor in accordancewith a third embodiment of the present invention.

FIG. 9 is a cross-sectional view of a high speed motor in accordancewith a fourth embodiment of the present invention.

FIG. 10 is a perspective view of a stator, shaft and cold plate used ina fifth embodiment of the present invention.

FIG. 11 is an exploded view of a hard disc drive of the presentinvention using the components of FIG. 10.

FIG. 12 is a perspective, partially cross-sectional view of amotor/generator for an electric vehicle using a liquid cooling channel.

FIG. 13 is a cross sectional view of the motor/generator of FIG. 12.

FIG. 14 is an exploded and partial cross sectional view of themotor/generator of FIG. 12.

FIG. 15 is an enlarged cross-sectional view of a portion of themotor/generator of FIG. 12.

FIG. 16 is a cross-sectional view of a motor in accordance with aseventh embodiment of the invention.

FIG. 17 is a cross-sectional view of a transformer in accordance withthe invention.

FIG. 18 is a cross-sectional view of a solenoid used in a fuel injectorin accordance with the invention.

FIG. 19 is a cross-sectional view taken along line 19-19 of FIG. 18.

FIG. 20 is a cross-sectional view of a solenoid flow valve in accordancewith the invention.

FIG. 21 is a perspective view of a heat transfer fluid confinementmember used in the valve of FIG. 20.

DETAILED DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENTS OF THEINVENTION

The term “electromagnetic field-functioning device” as used in thepresent application includes electromagnetic devices that include one ormore electrical conductors and use an electromagnetic field as part ofthe function of the device. In some embodiments, the device includes amoving part, and there is a relationship between movement of the movingpart and flow of current in the conductors involving one or moremagnetic fields. For example, in some devices, such as a motor orsolenoid, current in the one or more conductors generates one or moremagnetic fields, which generate a force that causes movement of themoving part. In other devices, such as a generator, the moving partgenerates a moving magnetic field, which in turn induces an electricalcurrent in the one or more conductors. In some devices, liketransformers, current conducted by the one or more conductors creates amagnetic field, and the magnetic field induces a current in a secondconductor coupled to the magnetic field.

The term “heat transfer fluid” as used in the present applicationincludes both liquids and gases, as well as combinations thereof. Whileliquids typically have a higher heat capacity per unit volume, and willtherefore be more frequently used in the present invention, gases, suchas air, may also serve as heat transfer fluids.

First Embodiment

A first embodiment of a motor of the present invention is shown in FIGS.2-4. The motor may be a “high speed” motor, meaning that the motor canoperate at over 5,000 rpm. The motor 10 is designed for rotating a discor stack of discs in a computer hard disc drive. Motor 10 is formedusing an encapsulation method which reduces the number of parts neededto manufacture the motor as compared with conventional motors used fordisc drives, thereby reducing stack up tolerances and manufacturingcosts and producing other advantages discussed below.

Referring to FIG. 2, a stator 20 is first constructed, usingconventional steel laminations 11 forming a magnetically inducible core17 having a plurality of poles 21 thereon, and wire windings 15 whichserve as conductors. The conductors induce or otherwise create aplurality of magnetic fields in the core when electrical current isconducted through the conductors. In this embodiment, a magnetic fieldis induced in each of the poles 21.

The stator 20 is then used to construct the rest of the motor 10 (FIG.3). The motor 10 includes a hub 12, which serves as a disc supportmember, the stator 20, a heat transfer fluid confinement member 62 and abody 14. Together the stator 20 and body 14 make up a stator assembly13. The heat transfer fluid confinement member 62 constitutes a heatpipe in the embodiment of FIGS. 2-4. The heat pipe has an annular shape.Heat pipes function by containing a fluid that carries heat from ahigh-temperature region to a low-temperature region, and then migratesback to the high-temperature region to repeat the cycle. Many heat pipesinclude a liquid that vaporizes at the temperature encountered in thehigh-temperature region, and travels as a gas to the low-temperatureregion, where it condenses. The heat pipes preferably include aninternal capillary structure, such as a wick, saturated with the workingfluid. As heat is input at the high-temperature region (sometimesreferred to as the evaporator), fluid is vaporized, creating a pressuregradient in the heat pipe. This pressure gradient forces the vapor toflow along the pipe to the low-temperature region, where it condenses,giving up its latent heat of vaporization. The working fluid is thenreturned to the evaporator by the capillary forces developed in the wickstructure. The heat pipe is sealed to prevent loss of the heat transferfluid. A heat pipe is thus one example of a heat transfer fluidconfinement member comprising a heat transfer fluid in a sealed system.Heat pipes can be built in a variety of shapes. The internal structureof the heat pipe 62 is not shown, but may be of any known arrangement,optimized for the expected operating temperature of the motor.

The body 14 is preferably a monolithic body 14. Monolithic is defined asbeing formed as a single piece. The body 14 substantially encapsulatesthe stator 20. Substantial encapsulation means that the body 14 eitherentirely surrounds the stator 20, or surrounds significant areas of thestator that may be exposed. However, substantial encapsulation meansthat the body 14 and stator 20 are rigidly fixed together, and behave asa single component with respect to harmonic oscillation vibration.

The body 14 is preferably formed of a phase change material, meaning amaterial that can be used in a liquid phase to envelope the stator, butwhich later changes to a solid phase. There are two types of phasechange materials that will be most useful in practicing the invention:temperature activated and chemically activated. A temperature activatedphase change material will become molten at a higher temperature, andthen solidify at a lower temperature. However, in order to be practical,the phase change material must be molten at a temperature that is lowenough that it can be used to encapsulate a stator. Preferredtemperature activated phase change materials will be changed from aliquid to a solid at a temperature in the range of about 200 to 700° F.The most preferred temperature activated phase change materials arethermoplastics. The preferred thermoplastic will become molten at atemperature at which it is injection-moldable, and then will be solid atnormal operating temperatures for the motor. An example of a phasechange material that changes phases due to a chemical reaction, andwhich could be used to form the body 14, is an epoxy. Other suitablephase change materials may be classified as thermosetting materials.

As shown in FIG. 4, a shaft 16 is connected to the hub or disc supportmember 12 and is surrounded by bearings 18, which are adjacent againstthe body 14. A rotor or magnet 28 is fixed to the inside of the hub 12on a flange so as to be in operable proximity to the stator. The magnet28 is preferably a permanent magnet, as described below. The body 14includes a base 22. In addition, mounting features, such as apertures 25(FIG. 3), and terminals comprising a connector 26 for connecting theconductors to an external power source are formed as a part of thestator assembly. The terminals 26 are partially encapsulated in the body14.

The heat pipe 62 is positioned in the body 14 so that one end is nearthe stator 20, which will be the high-temperature region. The other endhas one face that is not covered by the phase change material. This faceis located just below the hub 12, so that air currents created by thespinning hub can convey heat away from the exposed face, which serves asthe low-temperature region. The heat pipe 62 is substantiallyencapsulated in the body 14, as the body 14 surrounds almost all of theheat pipe 62 except for the minor exposed face, and the body 14 and heatpipe 62 are rigidly fixed together, and behave as a single componentwith respect to harmonic oscillation vibration.

Referring to FIGS. 3-4, the base 22 of the body 14 is generallyconnected to the hard drive case (not shown). Connecting members (notshown), such as screws, may be used to fix the base 22 to the hard drivecase, using holes 25 as shown in FIG. 3. Alternatively, other types ofmounting features such as connecting pins or legs may be formed as partof the base 22. The connector 26 is preferably a through-hole pin typeof connector 26 and is coupled through the hard drive case to thecontrol circuit board residing on the outer surface of the base (notshown). Alternatively the connector may be a flexible circuit withcopper pads allowing spring contact interconnection.

The stator 20 is positioned in the body 14 generally in a directionperpendicular to an interior portion 30. Referring to FIG. 2, the stator20 is preferably annular in shape and contains an open central portion32. The poles 21 extend radially outward from this central portion 32.Faces of the poles 21 are positioned outward relative to the centralportion 32 of the stator 20. The body 14 is molded around the stator 20in a manner such that the faces of the poles are exposed and aresurrounded by and aligned concentrically with respect to the discsupport member 12. Alternatively, the poles may be totally encapsulatedin body 14 and not be exposed.

Referring to FIG. 4, the body 14 has an upper portion 40 that extendsupwardly from the stator 20. The upper portion 40 is also preferablyannular shaped. The body 14 includes the interior portion 30. Theinterior portion 30 is generally sized and shaped to accommodate thebearings 18. The interior portion 30 includes an upper support portion42 and a lower support portion 44. In the embodiment illustrated in FIG.4, the interior portion 30 is preferably cylindrically shaped.

The phase change material used to make the body 14 is preferably athermally conductive but non-electrically conductive plastic. Inaddition, the plastic preferably includes ceramic filler particles thatenhance the thermal conductivity of the plastic so that it has acoefficient of thermal expansion similar to that of the heat pipe. Inthat way, as the encapsulated product changes temperature, either fromcooling after been molded, or heating during operation, the body 14 willstay in close contact with the heat pipe, but will not expand faster andcause pressure on the heat pipe, or thermal hardening of the walls ofthe heat pipe. If the thermoplastic body and heat pipe were to separate,there would be a significant barrier to thermal conductivity across thatjuncture.

A preferred form of plastic is polyphenyl sulfide (PPS) sold under thetrade name “Konduit” by General Electric Plastics. Grade OTF-212-11 PPSis particularly preferred. Examples of other suitable thermoplasticresins include, but are not limited to, thermoplastic resins such as6,6-polyamide, 6-polyamide, 4,6-polyamide, 2,12-polyamide,6,12-polyamide, and polyamides containing aromatic monomers,polybutylene terephthalate, polyethylene terephthalate, polyethylenenapththalate, polybutylene napththalate, aromatic polyesters, liquidcrystal polymers, polycyclohexane dimethylol terephthalate,copolyetheresters, polyphenylene sulfide, polyacylics, polypropylene,polyethylene, polyacetals, polymethylpentene, polyetherimides,polycarbonate, polysulfone, polyethersulfone, polyphenylene oxide,polystyrene, styrene copolymer, mixtures and graft copolymers of styreneand rubber, and glass reinforced or impact modified versions of suchresins. Blends of these resins such as polyphenylene oxide and polyamideblends, and polycarbonate and polybutylene terephthalate, may also beused in this invention.

Referring to FIG. 4, the bearings 18 include an upper bearing 46 and alower bearing 48. Also, each bearing 18 has an outer surface 50 and aninner surface 52. The outer surface 50 of the upper bearing contacts theupper support portion 42 and the outer surface 50 of the lower bearing48 contacts the lower support portion 44. The inner surfaces 52 of thebearings 18 contact the shaft 16. The bearings are preferably annularshaped. The inner surfaces 52 of the bearings 18 may be press fit ontothe shaft 16. A glue may also be used. The outer surface 50 of thebearings 18 may be press fit into the interior portion 30 of the body14. A glue may also be used. The bearings in the embodiment shown inFIGS. 3-4 are ball bearings. Alternatively other types of bearings, suchas hydrodynamic or combinations of hydrodynamic and magnetic bearings,may be used. The bearings are typically made of stainless steel.

The shaft 16 is concentrically disposed within the interior portion 30of the body 14. The bearings 18 surround portions of the shaft 16. Asdescribed above, the inner surfaces 52 of the bearings are in contactwith the shaft 16. The shaft 16 includes a top portion 54 and a bottomportion 56. The top portion 54 of the shaft 16 is fixed to the hub 12.The bottom portion 54 of the shaft 16 is free to rotate inside the lowerbearing. Thus, in this embodiment, the shaft 16 is freely rotatablerelative to the body 14. The shaft 16 is preferably cylindrical shaped.The shaft 16 may be made of stainless steel.

Referring to FIG. 4, the hub 12 is concentrically disposed around thebody 14. The hub 12 is fixed to the shaft 16 and is spaced apart fromthe body 14. The hub 12 includes a flux return ring 58 and the magnet28. The flux return ring 58 is glued to the disc support member. Themagnet 28 is glued to the hub 12. As shown in FIG. 4, the magnet 28concentrically surrounds the portion of the body 14 that includes thestator 20. In this embodiment the magnet 28 and stator 20 are generallycoplanar when the motor 10 is assembled.

The magnet 28 is preferably a sintered part and is one solid piece. Themagnet 28 is placed in a magnetizer which puts a plurality of discreteNorth and South poles onto the magnet 28, dependant on the number ofpoles 21 on the stator 20. The flux return ring 58 is preferably made ofa magnetic steel. The hub is preferably made of aluminum. Also, the hubmay be made of a magnetic material to replace the flux return ring.

As shown in FIGS. 3 and 4, the heat pipe may comprise just onecircumferential loop. Of course multiple heat pipes or pipe loops couldbe provided in the body 14.

Operation of the First Embodiment

In operation, the motor shown in FIGS. 3-4 is driven by supplyingelectrical pulses to the connector 26. These pulses are used toselectively energize the windings 15 around the stator 20 poles 21. Thisresults in a moving magnetic field. This magnetic field interacts withthe magnetic field generated by the magnet 28 in a manner that causesthe magnet 28 to rotate about the body 14. As a result, the hub 12begins to rotate along with the shaft 16. The bearings 18 facilitate therotation of the shaft 16.

The coolant is captive to the system and continuously recirculatesthrough the hollow structure of the heat pipe 62.

Method of Making the First Embodiment

The motor 10 shown in FIGS. 3 and 4 is made in part using anencapsulation technique. This encapsulation technique involves thefollowing steps, and uses the mold shown in FIGS. 5 and 6. First, a moldis constructed to produce a part with desired geometry. The mold has twohalves 72 and 74. Also, core pins 76 and 64 are connected to a plate 78that is activated by hydraulic cylinders 77 within the mold tool. Thestator 20 and heat pipe are placed within the mold and the two halvesare closed. The core pins hold the heat pipe at a predetermined distancefrom the stator 20. Second, using solid state process controlledinjection molding, plastic is injected through gate 80 around the stator20 and heat pipe 62 so as to encapsulate the stator and form the body 14shaped as shown in FIGS. 3 and 4 with the heat pipe 62 inside of it. Asplastic flows in, pins 76 are withdrawn so that the plastic completelysurrounds the stator 20, and pins 64 are withdrawn so that the plasticcan cover all but the end surface of heat pipe 62.

The pressure of the injection molding operation should be controlled tonot deform or damage the heat pipe. In other embodiments, discussedbelow, the pressure must be controlled so as to not crush a conduitfilled with ice or wax. For a full description of a process which may beused to control the pressure, attention is drawn to U.S. Pat. No.6,911,166. A summary of the information on col. 7 line 62 to col. 9,line 43 of the '166 patent follows.

An injection molding machine is used which is similar to the machinesused conventionally in thermoplastic injection molding processes. Aunique aspect, however, is the method for injection molding a phasechange material. The injection molding apparatus suitable for use in themethod comprises an injection cylinder having a resin feeding screwinside, a mold cavity, a runner, a stroke sensor and three pressuretransducers.

The molten material flows into the mold cavity via the runners. Gatesare placed at the end of the runner to control the flow of moltenmaterial into the mold cavity. A valve gate opens and closes the runnerto the cavity. Suitable valve gates are any valves known in theinjection molding art. However, it is also possible to perform themethod without the use of a valve gate. In a process where no valvegates are used, the molten material is kept at a predetermined pressurein the mold cavity and is allowed to solidify. The mold cavity is openedand the part and the solidified material in the runner are ejected andthen separated. The use of a valve gate eliminates the need for theseparating step.

The injection molding method begins with closing the mold cavity asillustrated in FIG. 6 and opening the valve gates. Molten material fillsthe cavity. A stroke sensor measures the rate of plastic injection. Acontroller correlates this rate, the compressibility of the plastic andthe size of the injection unit to determine a quantity of plasticinjected with time. A first pressure transducer is associated with thebeginning-of-fill point and is placed near the gate of the mold cavity.The beginning-of-fill point is the first portion of a mold cavity thatis filled by molten material. Thus, the first pressure transducer ispreferably placed within the first ten percent of the mold cavity to befilled by molten material. A second pressure transducer is associatedwith the end-of-fill point in the cavity. The end-of-fill point is thelast portion of a mold cavity that is filled by molten material. Thus,the second pressure transducer is preferably placed within the last tenpercent of the mold cavity to be filled by molten material. Also a thirdpressure transducer is placed in the runner to monitor the runnerpressure. The stroke sensor measures the fill rate of the molten phasechange material.

Molten material enters through the gate and quickly fills up the entirecavity. The stroke sensor and pressure transducers transmit theirrespective readings to a controller. The controller uses the pressureand stroke readings to determine whether to increase or decreaseinjection pressure and fill rate to achieve a desired fill profile andpressure gradient. Additionally the controller can be used to close thevalve gate and to stop the flow of molten material into the cavity. Thecontroller reduces the flow of molten material when the pressure at theend-of-fill point inside the cavity reaches a set point pressure. Ifvalve gates are not utilized, the controller maintains a constantinjection pressure until the material in the runner and mold cavity hassolidified. When the pressure at the end-of-fill point inside the cavityreaches the set point pressure, the molten material is allowed to cooland solidify. Although the embodiment described above uses only onecavity, it is contemplated that multiple mold cavities maybe utilized.

It will be understood that each step of the process can be implementedby computer program instructions or can be done manually. The computerprogram instructions may be loaded onto a computer or other programmabledata processing apparatus to produce a machine, such that theinstructions which execute on the computer or other programmable dataprocessing apparatus create means for implementing the desiredfunctions. These computer program instructions may also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture. The computer programinstructions may also be loaded onto a computer or other programmabledata processing apparatus to cause a series of operational steps to beperformed on the computer or other programmable data processingapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide steps for implementing the desired functions.

Besides injection molding of traditional thermoplastic materials,casting, roto-molding, reaction injection molding, compression molding,blow molding or combinations of these approaches may be used to makeproducts of the present invention. For example, CBT resins from CyclicsCorporation, 2135 Technology Drive, Schenectady, N.Y. 12308, can beprocessed using reaction injection molding or casting to make themonolithic body. These are polybutylene terephthalate (PBT) resinsystems that polymerize reactively like thermosets but have the materialproperties of thermoplastics, and hence produce monolithic bodies ofthermoplastic material. CBT® resins come in one and two partsystems—one-part systems where resin and catalyst are pre-mixed beforeprocessing, and two-part systems where resin and catalyst are mixedduring processing. They can have very high filler loadings (see U.S.Pat. No. 6,960,626, incorporated herein by reference), yet be injectionmolded at low pressures, which make them ideal for encapsulatingdelicate electromagnetic parts. Higher levels of filler can result inbetter thermal conductivity, coefficients of linear thermal expansionthat are closer to those of parts that are being encapsulated, andbetter vibration dampening. Low mold pressures also make it possible touse molds out of materials that are easier to shape than metal. Forexample, stereo lithography can be used to make intricate moldconfigurations very quickly and inexpensively, yet the resulting moldscan be used to make injection molded parts.

After the stator assembly is formed, the shaft 16 is press fit andpossibly glued into the bearings. Next, glue is placed on the outerbearing surfaces and the bearings and shaft are press fit into theinterior portion 30 of the plastic body 14. It may be desirable to moldthe interior portion 30 smaller than necessary and hone after themolding step to create a precise dimension for bearing insertion for thebearings being used. Next the aluminum disc support member 12 ismachined and the magnet and flux return ring are glued onto the lowersurfaces. The disc support member 12 is then glued to the motor shaft.

After the spindle motor and hub are assembled they can be used toconstruct a hard disc drive by using the holes 25 to mount the motor tothe base of the hard disc drive. Thereafter, construction of the harddisc drive can follow conventional methods.

Advantages of the First Embodiment

An advantageous feature of the first embodiment is provided by the factthat the body 14 is preferably a monolithic body 14 or monolithicallyformed using an encapsulation technique. This monolithic body 14provides a single structure that aligns the stator, and heat piperelative to one another, and causes good heat transfer between thestator and the hot portion of the heat pipe. (The use of multiple partsin previous devices results in stack up tolerances and increasedmanufacturing costs. Conversely, the single unitized body of the presentinvention provides alignment for the components of a motor and couplesthese components to one another.) By encapsulating the body 14, andthereby molding some components as part of the body 14 and using thebody to align the remaining components, stack up tolerances aresubstantially reduced, along with manufacturing costs. This also leadsto greater motor efficiency and performance. Further, the body 14 willbe cooled by the working fluid in the heat pipe 62, thus furtherproviding a lower operating temperature for the motor.

The disclosed motor optimizes dimensional tolerances among motorcomponents and thereby enables higher rotational speeds. The heatexchange mechanism of the heat pipe carries away the heat generated inthe stator when operating at those higher speeds. The fact that thepreferred body is made of thermoplastic allows the use of a type ofthermoplastic with a coefficient of linear thermal expansion (CLTE)similar to that of the heat pipe, and possible the same as other motorcomponents. As the motor heats up, and the exterior of the heat pipegets hot, the thermoplastic will expand at a rate similar to the heatpipe, eliminating any stress. As mentioned above, it is important not tohave disassociation of the thermoplastic to the heat pipe, which wouldthus create a gap which inhibits heat transfer. Further, it is importantnot to “work harden” the exterior of the heat pipe causing it to stresscrack.

As discussed above, controlling heat dissipation in conventional motorsis difficult to achieve. A particular thermoplastic may be chosen forencapsulating the body 14 that is designed to facilitate heatdissipation. By putting this material in intimate contact with the twoheat sources (motor windings and bearing) and then creating a solidthermal conductive pathway to the heat pipe, overall motor temperaturemay be reduced. The fact that these inserts are encapsulated within thebody, as opposed to being separately attached, simplifies themanufacturing process and allows for post machining, enabling moreprecise tolerances and ensures that dimensional consistency will bemaintained over the life of the motor.

The disclosed motor also offers superior performance in adverseenvironments. This is achieved because components such as the stator andheat pipes are substantially or completely encapsulated inthermoplastic. If the motor comes in contact with materials which couldcorrode the conductors, laminations or heat pipes, the phase changematerial in the form of a thermoplastic protects them. Further materialssuch as glue used to attach components together are eliminated throughthe use of a monolithic body 14.

Other embodiments of the invention my utilize encapsulation of more thanjust the stator and the heat pipe. For example, the entireelectromagnetic device or piece of equipment into which it is built maybe encapsulated to protect it from a corrosive environment, such as afluid pump immersed in liquid ammonia, or an electromagnetic device inan environment where ammonia vapor may condense.

Other embodiments of the invention may incorporate one or more “inserts”into the monolithic body of phase change material. In general, the term“insert” is used to describe any component other than the conductor andinductor that are substantially encapsulated in the phase changematerial. Different inserts may be used to provide different benefits.The inserts may be used to provide structural rigidity, thermalconductivity, vibration dampening or enhanced magnetic effect. Theinserts may themselves be magnetic. These second magnets can beenhancement magnets, which are directly involved with theelectromechanical functioning of the motor, or can be parts of amagnetic bearing (described in more detail below). The inserts mayenhance heat transfer away from the bearing and stator. The inserts mayenhance dampening of motor vibration. This may reduce audible noise aswell as improve motor life and allow for closer data track spacing.

In the embodiment of FIG. 7, there are two inserts. Specifically, acentral insert 260 in the form of an annular heat pipe is molded withinthe upper portion 240 of the body 214. The central insert 260 is moldedconcentrically with respect to the upper portion 240. A base insert 262,in the form of a hollow disc, is molded within the base 222 portion ofthe body 214. The central insert 260 and the base insert 262 serve toenhance the stiffness of the body 214. These inserts may also beinternally formed to operate as heat pipes, which will improve theoverall thermal conductivity of the body 214, and thereby improve motorperformance. The inserts may also be used in combination with the bodyof phase change material being a thermoplastic having properties whichallow it to dampen unwanted vibrations or audible noise. The plasticbody 214 locks the inserts into position with a high degree of strength.These inserts may be entirely overmolded by plastic or alternativelyportions of these inserts may be exposed. The motor 210 further includesstator 220, bearings 218, a rotor 212 with a shaft 216, magnet 228 andflux return ring 258.

Referring to FIG. 8, another embodiment of a motor 610 is shown. Thisembodiment includes similar components as the previous embodiments andin particular to the first embodiment. A monolithic body 614 is formedaround stator 620 using an encapsulation method. The primary differencebetween this embodiment and the first embodiment is that the bearings618 are spaced a substantially greater distance apart from the shaft 616than the bearings 18 in the first embodiment. This spacing is achievedusing an upper insert 670 and a lower insert 672 substantiallyencapsulated by the body 614. These inserts are preferably annularshaped, and act as extensions of the shaft 616. The upper insert 670 andthe lower insert 672 have hollow chambers and can be constructed as heatpipes. In this embodiment, the shaft 616 is fixed to the body 614,partially by being fixed to the inserts. An additional advantage of thisembodiment is that oversized bearings may be used. These larger bearingsgenerally have a longer life and can be run at higher speeds for longerperiods of time. These larger bearings more effectively dissipate heatfrom the bearing surface.

Another major advantage of this embodiment stems from the lower bearingbeing positioned on the lower section of the hub. This arrangementdramatically increases stiffness and reduces wobble during rotation. Theinserts 670 and 672 also provide stiffness and are thermally conductiveto dissipate heat.

In this embodiment rather than using metal inserts, cavities can beformed through lost wax casting, the cavities later being used aschambers for heat transfer fluids. Although such castings haverelatively poor dimensional consistency, when the castings are placed inthe mold in which the thermoplastic will be injected, the mold alignsthe parts and the thermoplastic is easily molded to have the requiredexternal geometry. Thus the final part can be made to very closetolerances. Utilizing the invention, the mold and thermoplastic offsetthe need for repeatability in the casting size and shape. The resultingcavity can then have a heat transfer fluid and the cavity sealed, asdescribed more fully with respect to the embodiment of FIG. 17 below.

Another embodiment of the invention is an axial flux motor, shown inFIG. 9. This embodiment includes a monolithic body 714 formed from anencapsulation method. The monolithic body substantially encapsulates acircuit board 721. Copper traces (not shown) are placed on the circuitboard and serve as the conductors that create a plurality of magneticfields. However, no steel core is used in this type of stator. Passingcurrent through the traces generates magnetic fields which cooperatewith fields in permanent magnet 728 attached to a rotor 712 to rotatethe permanent magnet 728 and thereby rotate the disc support member 712,supported by bearings 718 on shaft 716. The circuit board is preferablya multilevel circuit board. A cold plate 720 is encapsulated into thebottom of the assembly. Cold plates (also known as heat pipe integratedslim cold plates) are available from Enertron, Inc. 2915 N. Nevada St.,Chandler, Ariz. 85225.

Another embodiment of the invention is a hard disc drive 1102 shown inFIGS. 10 and 11. The motors of the previous embodiment were designed tobe manufactured separately and attached to the base or other housingcomponents of a hard disc drive. In this embodiment, the base 1134 ofthe hard disc drive is made as part of an assembly that alsosubstantially encapsulates the stator 1120. In this embodiment, a coldplate 1140 is also substantially encapsulated in the base. Even thoughthe cold plate 1140 is covered by thermoplastic material on only onesurface, it is a large surface, thus rigidly fixes the cold plate intothe base. Thus the stator 1120 and cold plate 1140 are integrallyconnected together with good heat conduction away from the stator. Inaddition, the base of the hard disc drive may be made with detailsmolded into the monolithic body such that the base can be used to easilyform the part of the case for the device and support other internalcomponents and provide in internal geometry required for operation ofthe part. While the embodiment disclosed in FIGS. 10 and 11 is for ahard disc drive, it will be readily apparent that the same concepts canbe used to make housing parts for other consumer electronic devices,like a camera, cell phone, PDA, portable digital music player, portablevideo player and the like, that have an electromagneticfield-functioning device that generates heat during operation.

The stator 1120 with windings 1122 and shaft 1116 (FIG. 10) arepreferably included into the base assembly 1134 (FIG. 11) when the bodyof phase change material is formed, such as by injection molding. Ofcourse, the shaft 1116 could be added to the base assembly afterwards.Preferably, the body of phase change material is a monolithic body ofthermoplastic material. The base assembly also preferably includes asecond shaft 1126 supported by the body of phase change material. Thissecond shaft 1126 is used to support the read/write head 1124 inoperable proximity to one or more discs 1114 supported on hub 1112. Thehub 1112 has a magnet 1128 connected thereto which is located inoperable proximity to the stator 1120 when the hub is rotatablysupported by bearing 1118 on shaft 1116. The hard disc drive 1102preferably includes other components, such as a circuit board 1130,wiring, etc. that is commonly used in hard disc drives and therefore notfurther described. Of course, a cover 1132 is preferably included andattached to the base assembly by conventional methods. The cover and thebase assembly cooperate to form a housing for the hard disc drive 1102.

One advantage of this embodiment of the invention is that the motor isbuilt directly onto the base assembly, which also includes the coldplate, reducing the number of parts. Further, the other components ofthe hard disc drive can be aligned with the motor and disc or discssupported thereon.

As can be seen from the forgoing, electromagnetic field-functioningdevices often include one or more, and generally a plurality, of solidparts used within the body of phase change material, such as bearingsand inserts. In addition, there are solid parts that are near the body,such as a disc support member and a hard disc drive base. Preferably thephase change material used to make the body will have a CLTE such thatthe phase change material contracts and expands at approximately thesame rate as the one or more solid parts. For example, the preferredphase change material should have a CLTE of between 70% and 130% of theCLTE of the parts substantially encapsulated in it. The phase changematerial should have a CLTE that is intermediate the maximum and minimumCLTE of the solid parts where the body is in contact with differentmaterials. Also, the CLTE's of the body and solid part(s) should matchthroughout the temperature range of the device during its operation. Anadvantage of this method is that a more accurate tolerance may beachieved between the body and the solid parts because the CLTE of thebody matches the CLTE of the solid parts more closely.

Most often the solid parts will be metal, and most frequently steel,copper and aluminum. The solid parts could also include ceramics. Inalmost all motors there will be metal bearings. Thus the phase changematerial used to encapsulate motor parts should have a CLTEapproximately the same as that of the metal used to make the bearings.

Most thermoplastic materials have a relatively high CLTE. Somethermoplastic materials may have a CLTE at low temperatures that issimilar to the CLTE of metal. However, at higher temperatures the CLTEdoes not match that of the metal. A preferred thermoplastic materialwill have a CLTE of less than 2×10⁻⁵ in/in/° F., more preferably lessthan 1.5×10⁻⁵ in/in/° F., throughout the expected operating temperatureof the motor, and preferably throughout the range of 0-250° F. Mostpreferably, the CLTE will be between about 0.8×10⁻⁵ in/in/° F. and about1.2×10⁻⁵ in/in/° F. throughout the range of 0-250° F. (When the measuredCLTE of a material depends on the direction of measurement, the relevantCLTE for purposes of defining the present invention is the CLTE in thedirection in which the CLTE is lowest.)

The CLTE of common solid parts used in an electromagneticfield-functioning device are as follows:

23° C. 250° F. Steel 0.5 0.8 (×10⁻⁵ in/in/° F.) Aluminum 0.8 1.4 Ceramic0.3 0.4

Of course, if the electromagnetic field-functioning device is designedwith two or more different solids, such as steel and aluminumcomponents, the CLTE of the phase change material would preferably beone that was intermediate, the maximum CLTE and the minimum CLTE of thedifferent solids, such as 0.64 in/in/° F. at room temperature and1.1×10⁻⁵ in/in/° F. at 250° F.

One preferred thermoplastic material, Konduit OTF-212-11, was made intoa thermoplastic body and tested for its coefficient of linear thermalexpansion by a standard ASTM test method. It was found to have a CLTE inthe range of −30 to 30° C. of 1.09×10⁻⁵ in/in/° F. in the X directionand 1.26×10⁻⁵ in/in/° F. in both the Y and Z directions, and a CLTE inthe range of 100 to 240° C. of 1.28×10⁻⁵ in/in/° F. in the X directionand 3.16×10⁻⁵ in/in/° F. in both the Y and Z directions. (Hence, therelevant CLTE's for purposes of defining the invention are 1.09×10⁻⁵in/in/° F. and 1.28×10⁻⁵ in/in/° F.) Another similar material, KonduitPDX-0-988, was found to have a CLTE in the range of −30 to 30° C. of1.1×10⁻⁵ in/in/° F. in the X direction and 1.46×10⁻⁵ in/in/° F. in boththe Y and Z directions, and a CLTE in the range of 100 to 240° C. of1.16×10⁻⁵ in/in/° F. in the X direction and 3.4×10⁻⁵ in/in/° F. in boththe Y and Z directions. By contrast, a PBS type polymer (Fortron 4665),was likewise tested. While it had a low CLTE in the range of −30 to 30°C. (1.05×10⁻⁵ in/in/° F. in the X direction and 1.33×10⁻⁵ in/in/° F. inboth the Y and Z directions), it had a much higher CLTE in the range of100 to 240° C. (1.94×10⁻⁵ in/in/° F. in the X direction and 4.17×10⁻⁵in/in/° F. in both the Y and Z directions).

In addition to having a desirable CLTE, the preferred phase changematerial will also have a high thermal conductivity. A preferredthermoplastic material will have a thermal conductivity of at least 0.4watts/meteroK using ASTM test procedure F433 and tested at roomtemperature (23.degree. C.).

Some electromagnetic field-functioning devices will have vibrations ofconcern, generally produced by harmonic oscillations. The phase changematerial can be selected so as to dampen oscillations at the harmonicfrequency generated by operation of the electromagneticfield-functioning device, many of which are dependent on theconfiguration of the windings or other conductors and any moving parts.In the case of a motor used in a hard disc drive, the phase changematerial will preferably have a vibration dampening effect so that themotor and disc assembly has a reduction of harmonic oscillations.

There are a number of properties of the phase change material that canbe varied in a way that will allow the phase change material to dampendifferent harmonic frequencies. This includes adding or varying theamount of glass, Kevlar, carbon or other fibers in the material; addingor varying the amount of ceramic filler in the material; changing thetype of material, such as from polyphenyl sulfide to nylon or otherliquid crystal polymers or aromatic polyesters, adding or graftingelastomers into a polymer used as the phase change material; and using adifferent molecular weight when the phase change material is a polymer.Any change that affects the flex modulus, elongation or surface hardnessproperties of the phase change material will also affect its vibrationdampening characteristics.

One way to determine the effectiveness of vibration dampening, and thusto select a suitable material, is to make up motor or other deviceconfigurations where different phase change materials are used, and thenmeasure the vibration dampening accomplished by each material. Thevibration dampening can be measured with a capacitance probe or laserDoppler vibrometer. In the range of 200-2000 Hz, and preferably in therange of 300-2000 Hz, the electromagnetic field-functioning device ofthe present invention will preferably have an amplitude decrease ofharmonic vibration of at least 5 and more preferably at least 10decibels. In the audible range, 20-15,000 Hz, the dampening willpreferably be at least 2, more preferably at least 5 decibels inreduction in harmonic frequency amplitude. These reductions are assessedbased on a comparison of the vibrations of the same electromagneticfield-functioning device but without the component being encapsulated.

As mentioned above, another use of the present invention is amotor/generator used as power source for a hybrid electric vehicle. Amotor/generator for such an application is shown in FIGS. 12-15. Themotor/generator 270 includes a stator assembly 272 and a rotatablymember, specifically a rotor 274, rotatably mounted to the statorassembly with bearings 276, specifically ball bearings. The statorassembly is made of core 273 made from steel laminations and providingpoles, and multiple conductors in the form of windings 278 that, whenthe device is acting as a motor, induce a plurality of magnetic fieldsin the core 273 when electrical current is conducted by the conductors.Of course when the devise is being used as a generator, the movingmagnetic fields induce an electrical current in the windings 278. Thestator assembly also includes two end brackets 280 and 282 that connectthe bearings 276 to the rest of the stator assembly. The laminationsmaking the core 273 and windings 278 are substantially encapsulated by abody 284 of phase change material. The body 284 has extensions 285 onone end that fit through holes 289 (FIG. 14) and are heat staked (FIG.13) to hold end bracket 280 onto the rest of the stator assembly.Terminals (not shown) connect the conductors 278 to a power supply orstorage source external to the motor/generator. The terminals arepartially encapsulated in the body 284.

The rotor 274 is hollow, and includes a hub 275 and a permanent magnet277 connected thereto in operable proximity to the stator when themotor/generator is assembled. The hub connects to the engine driveshaft, not shown. The outside diameter of the rotor 274 is smaller thanthe inside diameter of the open center of the stator assembly so thatthe rotor fits inside the stator assembly.

Two liquid-tight coolant channels 286 are also substantiallyencapsulated in the body 284 of phase change material. The channels 286may be molded into the body 284 when it is formed. A preferred method offorming the channels is to use a conduit that is put in place before thebody 284 is solidified. The conduit may be metal or thermoplastic. Inone embodiment the conduit is made out of the same thermoplasticmaterial that is used to injection mold the body 284. Preferably anyfittings 288 (FIGS. 14 and 15) needed to introduce and remove liquidfrom the coolant channels 286 are also partially encapsulated in thebody 284 of phase change material. A conduit can be used that has athreaded boss at the end, bent at an angle so that it terminates flushwith the end of the body 284, and the fitting 288 can be screwed intothe boss of the conduit. Alternatively, after the body is formed withthe coolant channels totally encapsulated, holes can be drilled throughthe bracket 282 and into the channels 286 and tapped so that thefittings 288 can screw into the stator assembly and establish a fluidcommunication with the coolant channels 286.

In a preferred embodiment, conduits filled with water or some otherfluid are frozen into a desired shape. These solid conduits are thenplaced in an injection mold cavity along with the windings 278 and thecore 273. Injection of thermoplastic material then fills the core to apredetermined plastic pressure and solidifies to form the body 284, withthe channels being left when the water originally frozen into theconduit is removed from the molded body.

FIG. 16 shows a motor 300 that utilizes two heat transfer fluidconfinement members, one formed as part of a cooling jacket (which isknown in the art) and one formed in a body of phase change material inaccordance with one aspect of the present invention. Motors with coolingjackets are known in the art. The motor 300 includes a hollow shaft 302to which a rotor 304 is attached by locking rings 306. The shaft isrotatably mounted to end brackets 308 and 310 by bearings 312. A stator314 is made with laminations 316 making up a core and wire 318 that goesaround the core to make multiple series of windings, allowing poles inthe stator to be energized in a repeating fashion to induce a magneticfield and cause the rotor 304 to rotate.

Surrounding the stator 314 is a cooling jacket like that known in theart. The cooling jacket 320 includes an aluminum body 322 and a sheetmetal cover 324. The aluminum body includes a plurality ofcircumferential channels 326 that tie into two manifolds 328, only oneof which is shown in FIG. 16, at the ends of the channels 326. Thechannels 326 and manifolds 328 are machined into the aluminum body 322before the sheet metal cover 324 is attached. Inlet 332 and outlet 324nipples are provided on the motor 300 to connect with a flow of coolingfluid. The cooling fluid flows into one of the manifolds from inlet 332,around the circumference of the cooling jacket through channels 326,then from the other manifold to outlet 334.

The motor 300 is modified from other known motors with cooling jacketsin that the stator is encapsulated with a body of phase change material336. The body 336 completely encases the wire windings 318. When thebody 336 is formed, preferably by injection molding, circumferentialchannels 338 are molded into the body near the end turns on the windings318. The aluminum body 322 is modified to include cross channels 340from the manifolds 328 to the channels 338 in body 336. In this manner,as a cooling fluid enters manifold 328 and flows through the channels326 in the cooling jacket, it will also flow through cross channels 340and then through the channels 338 which are located close to thewindings 318 where heat is generated, then back out through another setof cross channels to the other manifold and out through outlet 334.Preferably the phase change material making up body 336 will have highcoefficient of thermal conductivity, as described above, to aid theremoval of heat from the stator 314. Thus in this fluid-cooledelectromagnetic field-functioning device, a monolithic body of injectionmolded thermoplastic material substantially encapsulates the conductor,and a heat transfer fluid pathway is defined by at least one channel inthe monolithic body covered by a mating component, in this case thealuminum body 322. There are of course other modifications of thisaspect of the invention. Fluid channels could be formed by a mountingflange, or some other piece that forms an enclosure over a channel in abody of thermoplastic material. For example, in the motor/generator 270,fluid channels could be formed by molding channels, or machiningchannels after the molding, in the surface of the body 284 of phasechange material that will be covered by end bracket 280. Then the endbracket 280 could be secured in such a fashion that the bracket 280formed a mating component that sealed the channels, and thus definedfluid pathways.

Another embodiment of the motor 300 can be made with a coolant channelcooling the inductors in the rotor, either separately from, or inconjunction with cooling channels near the end turns of the windings. Insuch a device, a body of phase change material could be injection moldedaround the rotor 304. This body could include cooling channels, muchlike channels 338. Cooling fluid could be introduced through a hole inan end bracket 308 into the hollow shaft 302. Ports through the sidewall of the shaft would fluidly connect with the channels in the body ofphase change material encapsulating the rotor. Flow through the shaftand through those channels would provide good heat transfer from therotor to the heat transfer fluid, thus limiting the rise of thetemperature of the rotor.

FIG. 17 depicts a transformer 350 made according to the presentinvention. In this embodiment, the heat transfer fluid confinementmember is made as a chamber in a body of phase change material. Thechamber forms a sealed system. The transformer, as with othertransformers, includes two conductors, a primary coil 352 and asecondary coil 354, as well as a lamination stack 356 which provides aninductor. The body of phase change material 357 is molded around thelamination stack 356 and forms the outer housing of the transformer 350.The body 357 includes chamber 358, which contains a heat transfer fluid360. The monolithic body of thermoplastic material thus substantiallyencapsulates both the inductor and the heat transfer fluid confinementmember. The chamber is sealed by a lid 362. Holes 364 are providedthrough the lamination stack 356 for the migration of the heat transferfluid 360.

In operation, heat generated in the conductors causes the heat transferfluid 360 to vaporize and rise to the top of chamber 358. Since it iscooler in the top section, the heat transfer fluid condenses and runsback into the bottom of the chamber 358. The phase change material,having good heat transfer properties, helps to transfer the heat fromthe lamination stack 356 to the heat transfer fluid. The thicknesses ofthe side walls (not shown to scale in the drawing) will be designed sothat heat transfer up the walls will be minimized, thus keeping the wallsections near the lid 362, as well as the lid itself, at a coolertemperature, so that the heat transfer fluid can condense in the topportion of the chamber.

The chamber 358 in the transformer can be formed by injecting a gas intothe molten phase change material during molding of the body 357. U.S.Pat. No. 6,037,038, hereby incorporated herein by reference, discloses amethod of molding a hollow handle by injecting a fluid, such asnitrogen, through gas injection nozzles into a molten handle material.The same procedure may be used to form a hollow chamber having anon-linear shape for transformer 358. (By “non-linear” it is meant thatthe chamber or flow path cannot be formed by a simple core pin in aninjection mold tool.) A process of controlling injection moldingpressures described above and in U.S. Pat. No. 6,911,166 can be used totime the injection of the gas for coring and to determine theshape/position of the cavity formed by the gas. Alternatively, someother material (ice or wax) can provide a melting core to form thechamber 358.

After the chamber 358 is formed, and heat transfer fluid 360, such as analcohol or aromatic hydrocarbon, is added, the cap 362 is used to sealthe opening in the chamber. The cap can be either permanently installed,or a removable cap can be used if future replacement or addition of theheat transfer fluid 360 is contemplated. A plastic plug could be weldedin place using ultrasonic, sonic or vibration welding after the fluid isadded, or a metal cover could be attached with an O-Ring providingsealing at the interface.

FIGS. 18 and 19 depict a solenoid valve 400 which may, for example, bepart of a fuel injector. In this embodiment, the heat transfer fluid isa fluid, such as fuel, that is passing through the solenoid valve and isused for other purposes in addition to heat transfer. The valve includesa conductor 402 in the form of windings, a plunger 404, a metal shell406 and a body of phase change material 408. The plunger 404 includes afairly wide head 410, a seat 412 and a connecting rod 414. The body 408includes a plurality of fluid ports 416 running parallel to theconnecting rod 414. Molded in O-rings 418, 420 and 422 provide a shutoff sealing surface against which the seat 412 (in the open position) orthe head 410 (in the closed position) seals. In the open position (asshown) fuel can flow through the fluid ports 416.

The solenoid valve 400 may be constructed by forming (such as machining)the metal housing 406. The windings 402 are initially wound on a bobbin.The bobbin is then encapsulated by the body 408 of phase changematerial, leaving a central bore for connecting rod 414. The fluid ports416 are also left as openings through the body 408 of phase changematerial. Later the plunger 404 is assembled.

During operation, current is conducted through the windings 402, whichcreates a magnetic field, drawing plunger 404 into an open position. Aspring (not shown) is used to bias the plunger in a closed position.

The body 408 of phase change material provides good thermal conductivityfrom the windings 402 to the fluid passing through the fluid ports 416,and at the same time encapsulates the windings 402, protecting them fromcontact with the heat transfer fluid, which in this case may be a fuel.There is an additional benefit in that the fuel passing through thesolenoid is heated, which will make it easier to be vaporized prior tocombustion. The rest of the fuel injector is not shown or described, butoperates in a conventional manner.

A different solenoid valve 450 is shown in FIG. 20, and a part used toconstruct the valve is shown in FIG. 21. Like the valve 400, thesolenoid operated valve 450 is also cooled by a heat transfer fluid, theflow of which is controlled by the valve.

FIG. 21 shows a conduit 452 formed in a helical shape. The conduit 452may start out as an ice-filled tube. The valve 450 also includes aconductor 454 in the form of wire windings on a bobbin 456. The bobbin456, wire 454 and conduit 452 are placed in a mold and a phase changematerial, such as a thermoplastic, is molded around the pieces toencapsulate them and form a body 458. Water melted from the iceoriginally in the conduit is emptied after the molding operation. Acentral channel 460 is left for placement of a spring 462 and plunger464. An O-ring 466 is used to seal against the plunger 464 when thevalve is closed (as shown). Pipe threads 468 may be molded onto the body458 to form inlet 470 and outlet 472 connections.

Another embodiment of the invention is an electromagneticfield-functioning device for heating a fluid. Such a device includes atleast one electrical conductor that generates heat when in use, and amonolithic body of injection molded thermoplastic material substantiallyencapsulating the conductor. A fluid pathway is also provided in themonolithic body, with at least one fluid inlet and at least one fluidoutlet to allow for passage of fluid through the pathway. The outletdirects the fluid to a place of usage wherein heat picked up by thefluid as it is transferred through the device is put to functional use.

A good example of such a device is the solenoid of FIG. 18, in which thefuel passing through the device is heated to aid in vaporization of thefuel. Also, the solenoid valve 450 of FIG. 20 could be used in thismanner, if the fluid flowing through the device is directed from theoutlet to a place where heat picked up from the conductor 454 is put toa functional use. Another example of such a device is a water pumpwherein the motor is used to heat water flowing through the pump bypassing the fluid through the fluid pathway used to cool the conductorsof the motor. This heated water may be directed to a heated pool ofwater, such as a hot tub, Jacuzzi tub or swimming pool. U.S. Pat. No.5,172,754 discloses a heat exchanger for recovery of heat from a spa orhot tub pump motor. In the '754 patent, a heat exchange coil is wrappedaround the outside of a motor. Water flows from the discharge side ofthe pump, through this heat exchange coiling, and is mixed with coolerwater entering the pump. Rather than using a separate heat exchangecoil, one pump embodiment of the present invention utilizes a fluidpathway through a monolithic body that encapsulates the windings for thepump motor, much like the fluid pathway formed by conduit 452 used insolenoid valve 450.

The heat transfer fluid does not need to be a liquid. An air blower maybe powered by a motor, with air moved by the blower being directedthrough a fluid pathway formed in a monolithic body of phase changematerial substantially encapsulating the conductor (and/or inductor) ofthe motor powering the blower. The air would be heated by passingthrough the fluid pathway, and could then be directed to a place wherethe heat is put to a functional use, such as a breathing apparatus wherethe air is warmed before being directed to a patient. To further aid inheating the air, the bearings of the motor could also be encapsulated inthe monolithic body of phase change material.

Another embodiment of the invention is a fluid conveying mechanism, suchas a pump or blower, that integrates fluid ports into the samemonolithic body that encapsulates the conductor or inductor of theelectromagnetic field functioning device that powers the mechanism. Theelectromagnetic field-functioning device has at least one electricalconductor or inductor. A monolithic body of injection moldedthermoplastic material substantially encapsulates the conductor and/orinductor. A fluid pathway is provided in the monolithic body throughwhich at least a portion of the fluid conveyed by the mechanism passes.A fluid inlet port or outlet port, or both, are formed in the body ofinjection molded thermoplastic, and the pathway through the body isconfined within the body. Thus the pathway is a defined pathway througha housing that is formed, at least in part, out of the same monolithicbody that encapsulates the conductor or inductor.

Most prior art pumps are attached to a motor in such a way that animpeller is turned by a shaft. The motor and the impeller are indifferent housings, and a seal around the shaft keeps liquid beingconveyed by the pump from coming into contact with the components of thepump motor. U.S. Pat. No. 4,944,653 describes such a plastic pump motorassembly, where the motor is mounted in a cantilever fashion withrespect to a separate pump casing 37. The motor shaft extends through anopening 39 in the casing and a seal 64 prevents water leakage. Someembodiments of the invention make it possible to make a pump/motorassembly without a separate pump housing. The present invention can beapplied to a well pump. Through encapsulation, the motor can beinstalled inside the pump casing. The fluid transported by the pump cancirculate through apertures formed in the encapsulant. The benefit is asmaller structure that is quieter. The shaft/pump casing interface iseliminated. U.S. Pat. No. 6,659,737 (hereby incorporated herein byreference) discloses a pump that can be modified according to thepresent invention so that the thermoplastic encapsulating the statorbody is also used to form the housing for the device. In such anembodiment, the stator would be constructed without the shaft and heldon a core pin in a mold. The inside surface of the mold would form theoutside of the housing. The housing would have a larger inlet thandepicted in the '737 patent, one that would allow the motor shaft andimpeller to be added to the stator after the molding operation. The flowpath through the plastic could be formed by either injecting gas intothe molten plastic in the mold so/as to produce channels, or by moldingaround a plurality of conduits filled with ice or wax which could laterbe removed to leave an integrated flow path through the body. In eithermanner, a fluid inlet port and a fluid outlet port could be formed inthe body of injection molded thermoplastic, and the pathway through thebody would be confined within the body. Thus the pathway is a definedpathway through a housing that is formed, at least in part, out of thesame monolithic body that encapsulates the conductor. Rather than havinga two-part housing that is separately molded and attached to anencapsulated stator, one monolithic body would be formed thatencapsulates the stator and forms the flow channels through the device.

While the chamber for the transformer in FIG. 17 can be formed byinjecting a gas into the thermoplastic while it is injected into themold, other coolant channels for other electromagnetic field-functioningdevices may be formed in a similar manner. As the thermoplastic isfilling the tool, nitrogen is injected into the molten plastic to formthe hollow section in the shaft and create a hollow cavity that isconformal to the wire and laminations.

While exemplary methods of cooling the different devices have beendepicted in the drawings, the present invention contemplates using thevarious methods on other devices than those in which it is specificallyshown in the drawings. For example, while small spindle motors would nottypically be cooled by a liquid that flows into and out of the motor,there may be applications where this is practical. Then the coolingchannels shown in the devices of FIGS. 12-16 and 20-21 could be used inthe body of phase change material encapsulating the stator. The variouscooling techniques can be applied to relays, and other electromagneticfield-functioning devices. Likewise, motors could be made where chamberswere formed in the body of phase change material, a heat transfer fluidis added to the chamber, and the chamber sealed, like the transformer ofFIG. 17. Heat pipes and cold plates could be substantially encapsulatedin the phase change material encapsulating the conductors of devicesother than the motors of FIGS. 2-11. Rather than encapsulating theconductors and the heat exchange member together, in some devices aninductor will preferably be encapsulated with a heat exchange member,like the transformer of FIG. 17. Gas-assist molding, such as can be usedto make the chamber in the transformer of FIG. 17, can be used to formcooling channels or chambers in other products.

Where the heat exchange member involves a working fluid that isvaporized during operation of the device, such is in a heat pipe, or inthe chamber 358 in transformer 350, the working fluid will preferable bea heat transfer fluid substantially vaporizable at a temperature in therange of operating temperatures expected for the device, which willtypically be between about 25° C. and about 200° C. Of course thetemperature at which a liquid will vaporize is a function of thepressure at which the system is operating, which for sealed systems isusually also a function of temperature. However, the heat transfer fluidwill be chosen such that it will vaporize in this temperature range forthe expected internal pressure of the system in which it is used.

While the presently preferred embodiments utilize injection molding toform the monolithic bodies of phase change material, other methods ofmolding, such as blow molding, compression molding, casting,roto-molding, reaction injection molding or combinations of such methodsmay be used.

One unique aspect of the invention is that a variety of cooling channelsor heat pipes can be encapsulated in different parts made using the samemold tool. For example, heat pipes that vary with respect to one or moreof their dimensions, such as their diameter and/or their thickness, mayfit within the same mold tool. As a result, different heat pipes can beencapsulated and used to build a variety of motors or otherelectromagnetic filed functioning devices. Not only does this reduce thenumber of mold tools that are needed, but the final assemblies will havea final uniform size and shape, since the phase change material bodywill have the same dimensions for each. As a result, other components ofthe device, such as the housing, can be constant between differentproducts.

Following is a summary of some of the benefits of preferred embodimentsof the invention.

With coolant channels encapsulated in the body of phase change materialalso encapsulating the stator windings and core, heat generated in thestator can be easily removed by circulating a liquid through the coolingchannels. The liquid is totally contained, unlike air blown by a fanblade attached to a motor shaft. Motors using this invention thus can bemade smaller but run highly loaded, or at high speeds, with more turnsof finer wire. In the past such small motors would get too hot, but withthe present invention, and the improved methods of removing heat fromthe motor, this problem is eliminated.

A number of other ways to improve thermal conductivity are provided.First, the phase change material will itself provide some heatdissipation. Second, the phase change material can include additivesthat will enhance its thermal conductivity. Third, heat conductiveinserts can be included in the motor or other electromagneticfield-functioning device. Fourth, the body of phase change material, bybeing in contact with a number of parts of the motor and/or disc drive,can act as a pathway for heat such that those other parts of the motorand/or disc drive can act as heat sinks. This improved thermalconductivity provides longer life to the electrical and bearingcomponents of the device, with higher efficiency and lower current draw.If the device is a motor/generator used for a hybrid vehicle, it willalso provide the opportunity to create more electricity to power thedrive motor or recharge the batteries and improve overall fuelefficiency.

The encapsulation protects the windings from the environment, as well asthe liquid used to cool the motor, while offering the opportunity toheat a fluid in operable proximity to the electromagnetic device. Theuse of retracting positioning pins and gas injection allows completeencasement of components of the electromagnetic field-functioning deviceinside a layer of phase change material. For example, in themotor/generator used in a hybrid electric vehicle, the conductors areencased and protected from flying debris.

The present invention can be used with electromagnetic devices havinglaminated cores and wire windings. It can also be used on devices usingsintered inductive cores and permanent magnets as well as multilayercircuit board configuration or coils on a circuit board.

The device designs allow for unique manufacturing possibilities. Thelaminations and windings do not need to be separately cleaned and, oncethe assembly has been encapsulated, it will not generate contaminants.The device can be cleaned via ultrasonic cleaning, steam, chemicalsterilization, which is important in medical and food processingindustries. In addition, if inserts are encapsulated and then machinedto provide precise dimensions, one cleaning step can be used after allfabrication steps. It is not practical to do this type of machining onassembled parts without the present invention because there is nopractical way to clean the entire assembly after such a machiningoperation. Cellular manufacturing technology can be used. The device canbe made anywhere and then cleaned just before being assembled. There isno need for costly packaging to keep the assembly clean. Also, thedurability of the assembly allows for low cost shipping.

The use of an encapsulated stator allows the fluid connectors to beintegrated into the body. Separate fluid ports and reservoirs areunnecessary In general, the device can be more easily assembled and willinclude fewer parts. As noted above, the stack-up tolerances are reducedbecause components are eliminated and the tolerances associated withassembly operations disappear. The phase change material can be designedwith a CLTE that closely approximates that of other components. Bymatching CLTE, one also obtains better environmental conditions.Otherwise, plastics get microcracks during thermal cycling, which allowmoisture or other fluids to attack the encapsulated components.

There are a number of cost benefits associated with aspects of thepresent invention. There are cost benefits from fewer components. Themanufacturing process has reduced costs. The device can be smallerrequiring less copper or steel. Components do not need the same level ofdimensional precision. There are also benefits associated withdevelopment time and cost for electromagnetic configurations. Designimplementation can be faster. First, since there are fewer parts, lessparts have to be designed for each new motor. Second, fewer tools areneeded, since fewer parts are required. Third, injection molding toolsare modular in nature. This allows tooling to be easily customizedwithout requiring a redesign of the whole tool. In many cases, one toolcan be used for multiple product designs and iterations. For example,plastic molding tools might be able to be used with multiple coolingsystems.

It should be appreciated that the apparatus and methods of the presentinvention are capable of being incorporated in the form of a variety ofembodiments, only a few of which have been illustrated and describedabove. The invention may be embodied in other forms without departingfrom its spirit or essential characteristics. The described embodimentsare to be considered in all respects only as illustrative and notrestrictive, and the scope of the invention is, therefore, indicated bythe appended claims rather than by the foregoing description. Allchanges that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A fluid-cooled electromagnetic field-functioning device comprising:a) at least one electrical conductor; b) a monolithic body of injectionmolded thermoplastic material substantially encapsulating the at leastone conductor; and c) a mating component, wherein a heat transfer fluidpathway is defined by at least one channel in the monolithic bodycovered by the mating component, with at least one fluid inlet and atleast one fluid outlet to said pathway to allow for passage of heattransfer fluid through the pathway; wherein the monolithic body ofinjection molded thermoplastic material substantially encapsulates theone or more conductors and an inductor, and the one or more conductorscomprise wire windings in operable proximity to said inductor.
 2. Theelectromagnetic field-functioning device of claim 1 wherein the heattransfer fluid pathway is provided by at least one channel formed in anouter surface of the monolithic body of injection molded thermoplasticmaterial and the mating component comprises a mounting flange formounting the device.
 3. The electromagnetic field-functioning device ofclaim 1 wherein the heat transfer fluid pathway comprises a plurality ofchannels in the monolithic body.
 4. The electromagneticfield-functioning device of claim 1 wherein the device comprises amotor.
 5. The electromagnetic field-functioning device of claim 1wherein the device comprises a solenoid.
 6. The electromagneticfield-functioning device of claim 1 wherein the device comprises agenerator.
 7. The electromagnetic field-functioning device of claim 1wherein the device comprises a relay.
 8. The electromagneticfield-functioning device of claim 1 wherein the device comprises atransformer.
 9. The electromagnetic field-functioning device of claim 1wherein the conductor is part of a stator having multiple conductorsthat create a plurality of magnetic fields when electrical current isconducted by the conductors; and the body of thermoplastic materialsubstantially encapsulates the stator.
 10. A hybrid electric vehiclecomprising the device of claim
 1. 11. The electromagneticfield-functioning device of claim 1 wherein the device comprises a pump.12. A fluid cooled electromagnetic field-functioning device comprising:a) at least one electrical conductor; b) a monolithic body of injectionmolded thermoplastic material substantially encapsulating the at leastone conductor; and c) a mating component, wherein a heat transfer fluidpathway is defined by at least one channel in the monolithic bodycovered by the mating component, with at least one fluid inlet and atleast one fluid outlet to said pathway to allow for passage of heattransfer fluid through the pathway; wherein the heat transfer fluidpathway is provided by at least one channel formed in an outer surfaceof the monolithic body of injection molded thermoplastic material andthe mating component comprises a cooling jacket around the monolithicbody, the cooling jacket including at least one heat transfer fluid flowpassageway in fluid communication with the at least one channel in themonolithic body.